1. Field of the Invention
This invention relates to a pervious concrete product of the type which allows liquid and particularly water to drain therethrough isotropically or in a substantially even distribution and the process of forming and distributing the resulting concrete product through transportation, mixing and distribution procedures and equipment which differ from conventional technique utilized in producing and forming Portland cement type concrete.
2. Description of the Prior Art
In the construction and building industry the term "concrete" is used generically to define a collection or aggregation of materials which together form a reasonably continuous solid. Prior art products include both natural concrete and a variety of synthetic concretes. The most common of such products being asphaltic concrete in which inert aggregates are mixed with a bituminous binding component, and Portland cement concrete. In Portland cement concrete the object is to obtain a continuous monolithic material of substantially uniform properties. In conventional and by far the majority of normal applications of concrete, voids and/or small discontinuities or inclusions of air are considered to be highly undesirable since these voids, etc. harmfully affect the operating or performance characteristics of the end concrete product.
However, in the specialized category of pervious or porous concrete such voids are intentional in the formation of the concrete product. While such porous concrete is generaly well known in the prior art, porous concrete suffers from inherent problems which make the overall product relatively undesirable. Such prior art porous concretes are generally considered of variable quality and indeterminate permability and thus unreliable or defective for controlled or specified construction applications.
The following U.S. Patents disclose prior art products and/or methods of forming concrete products or cementitious material which are generally applicable but clearly distinguishable from the product and process of the present invention, described hereinafter U.S. Pat. Nos.: 271,080, to Lynch; 358,288 to Moore; 1,665,104 to Martienssen; 3,196,122, to Evans; 3,240,736, to Beckwith; 3,360,493, to Evans; 3,439,450 to Richards; 3,477,979 to Hillyer; 3,687,021 to Hensley; 3,690,227 to Weltry; 3,870,422, to Medico; 2,130,498 to Klemschofski; and 3,822,229 to McMaster.
As evidenced by the prior art set forth above there is an obvious desirability and need for porous concrete products. Such products generally and/or theoretically would be much more efficient where drainage of water is desired pertinent to concrete product applications such as in highways, airports, parking facilities, bridge decks, etc.
However, products of the type disclosed in the above set forth U.S. patents frequently suffer from certain inherent disadvantages such as fracture when used under heavy load or stress conditions (commonly called ravelling) in roads, highways, and pavements where they are generally formed using substantially conventional concrete forming techniques or processes, with or without the application of additives to allegedly increase adhesion between the aggregate particles and improve other performance characteristics.
However, there is a great need in the construction and building industry, specifically in building roads, highways, etc. for a porous concrete having an even distribution of liquid flow therethrough and which can better provide for the load or stress conditions from high speed operation of automobiles or large vehicles such as trucks, airplanes or the like.